<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>4.关于函数的返回值</title>
  </head>
  <body>
    <script type="text/javascript" >
        function demo(){
          return setTimeout(() => {
            return 666
          }, 1000);
        }

        const x = demo()
        console.log(x)
    </script>
  </body>
</html>